2. INTRODUCTION OF STRING
► Incomputer programming, a string is
traditionally a sequence of characters, either
as a literal constant or as some kind of
variable A string is as a data type and is
often implemented as a byte (or word)
array that stores a sequence of elements,
typically charactersusing some
character encoding
3. STORING STRING
► Inc++ language,a string is stored in an array
of characters.It is terminated by the null (‘0’)
character.because string is stored in an
array,the name of the aaray, and hence
string, is a pointer to the beginning of the
string.For example “hello”
5. String Datatype
►A string datatype is a datatype
modeled
on the idea of a formal string . Strings are
such an important and useful datatype that
they are implemented in nearly never
programming language .In some language
they are avalible as primitive types and in
others as composite types
6. String Literals
►A string literal ,also known as string
constant ,is a sequence of characters
enclosed in double quotes.For example:-
“hello!you are welcome”
“”
“a”
7. String Variables
► A string variable is actually an array of
characters.
It has two types
3. Declaring string variables
4. Initializing string variables
8. STRINGS AND ASSIGNMENT
OPERATOR
► String is an array of characters , therefore,
the name of the array is a pointer constant ,
it is an rvalue, and therefore cannot be used
as the left operand of the assignment
operator.
► For example :- char strl[]= “hello”;
char str2[20];
str2=str1;
9. String lenght
► Although formal strings can have an arbitrary
length, the length of strings in real languages is
often constrained to an artifical maximaum . In
general, there are two types of string data type .
Fixed length strings , which have a fixed maximun
length and which use the same amount of memory
.whether this maximum is reached or not , and
variable length strings,whose length is not
arbitrarity fixed and which use varyingamounts of
memory depending on their actul size
10. Character string functions
► Stringfunction are used to manipulate a
string or change or edit the contents of a
string. They also are used to query
information about a string.they are usully
used within the content of a computer
programming language
11. Input/Output of String Data
There are approaches to perform input/output
of string data.these are two types:-
using character I/O functions
using string I/O functions
The input/output of string data can be
performed using character I/O functions as
illustrated in the following programs .
12. Program to perform input/output of string data with
character I/O functions of streams objects cin &cout
► #include<iostream.h>
► Void main()
► {
► Char str[30];
► Int I,n=0;
► Cout<<“n enter string of length <=29”;
► Cout<<“n and terminate with ENTER keynn”;
► While( (str[n]=cin.get() )!=‘n’)
► N++;
► Str[n]=‘0’
► Cout<<“n you have entered nn”;
► For(i=0;i<n;i++)
► Cout.put(str[i]);
► Cout<<“n”;
► }
13. Progarm to perform input/output of string data with
getline()function of cin stream object
► #include<iostream.h>void main
►{
► Char str[30];
► Cout<<“n enter string of length<=29;
► Cout<<“n and terminate with ENTER keynn”;
► Cin.getline(str,30);
► Cout<<“n you have entered nn”;
► Cout<<str;
► Cout<<“n”;
►}
14. The strlen() function:-This function
takes one argumentthat can be a string constant or
a variable. The counts the no. of character present
in the string. Do remember that null character ‘0’ is
not a part of the character, it is merely used to mark
the end of the string,so it is not counted
15. The strcat() function
► This function takes two arguments, of which
first is a variable and second can be a string
constant or a variable. It appends the
character(s) of the second arguments at the
end of the first argument. There must be
sufficient avaible to accommodate the
incoming character from destination
string,otherwise over flow occurs.
16. Program to illustrate the useof
strcat()function
► #include<iostream.h>
► #include<string.h>
► Void main()
► {
► Char str[30]=“wel”, str2[30]=“come”;
► Cout<<“n first string is “<<str1;
► Cout<<“nn second string after appending second one is
nn”;
► Cout<<str<<“n”;
► }
17. The strcpy() function
► Thisfunctions takes two arguments, of
which first is a string variable and second
can be a string constant or a variable. It
copies the characters of the second
argument to the first argument.
18. The strcmp() function
► This functions takes two arguments, of
which boyh can be string variables or
constants.It compares the characters of
each but one at a time and returns a value
indicating the result of the comparison.
► For example:-strcmp(str1,str2);
19. Passing string to a function
►A string can be passed as an argument to a
function using subscripted notation for
arrays.In a function definition, the formal
parameter is delared as an array of
cahracters.
20. Program to illustrate the passing of a string to
a function
► #include<iostream.h>
► #include<string.h>
► Void func(char[]); //function prototype
► Void main()
► {
► Char str1[]=“sample string’;
► Func(str1);
► }
► Void func(char temp[])
► {
► Cout<<“n string passed to it:”<< temp;
► Cout<<“nn its length is:”<<strlen(temp)<<“n”;
► }
21. Array of string
► In two-dimensional arrays,the first row
stores the first string, the second row stores
the second string.
► For example:-char names[4] [12];
22. Safe operations
► As we discuss before, string functions are
not safe in general since the size of the
string is not controlled(everything depend
upon the occurance of the null character)
23. Safe operations
►A solution is used in the safer functions:
► Strcmp(), strcat(), strcpy()
► strcmp(dest ,src,n): compare at mast n
character of dest
► Strcat(dest ,src,n): concatenate atmost n
character of scr to dest
► Strcpy(dest, scr, n):copy at most n
character of scr to dest
24. String processing
► Sscanf() is very similar to scanf(). The only
difference is that it takes the the input from
a string rather than the console.
► Sscanf(char*s, const char,* format,……..)
► For eg: char input-str[50];
► Int i; float f; char st[10];
